Android - How to regenerate R class? [duplicate]

Answer 1

This problem normally happens when importing from an existing project. Try to fix all errors from all .xml files in res folder, as well as Manifest file. Most likely the errors are shown at "match_parent" parameter, change it to "fill_parent". When all errors are clear, R.java will be appeared.

If there is no error on any .xml file. Try edit any xml file (like delete a letter and type it back) and then save the file, this will cause to generate the R.java.

Answer 2

I found this happening to me with a broken layout and everything blows up. Relax, it's like that old mistake when you first learned programming where you forget one semicolon and it generates a hundred errors. Many panic, press all the buttons, and makes things worse.

Solution

• Make sure that anything the R. links to is not broken. If it's broken, ADK may not regenerate R. Fix all errors in your XML files.
• If you somehow hit something and created import android.R in your activity, remove it.
• Run Project -> Clean. This will delete and regenerate R and BuildConfig.
• Make sure Project -> Build Automatically is ticked.
• Wait a few seconds for the errors to disappear.
• If it doesn't work, delete everything inside the /gen/ folder
• If it still doesn't work, try right-clicking your project -> Android Tools -> Fix Project Properties.

What to do if R doesn't regenerate

This usually happens when you have a broken xml file.

• Check errors inside your XML files, mainly within the /res/ folder
• Common places are /layout/ and /values/ especially if you've changed one of them recently
• Check AndroidManifest.xml, I find that often I change a string, and forget to change the string name from AndroidManifest.xml.
• If you can't find the issue. right click /gen/ -> Restore from local history... -> tick R.java -> click Restore. This doesn't solve the problem, but it will clear out the extra errors to make the problem easier to find.

I know there's already a lot of answers here, but this is the first link on Google, so I'm compiling all the advice here and hope it helps someone else new to this :)

Answer 3

I had a similar problem where the R.java file was not being regenerated after I'd added some icons and layout files. I tried cleaning and rebuilding and things got worse since then the original R.java file was gone and still wasn't regenerated. Eventually it dawned on me that there must be compiler errors for the compiler that generates R.java and we aren't being shown those in the console. Fortunately, I had noticed earlier that

1. it's an error if one .xml file refers to another which is non-existent and
2. it's an error to have upper case letters in your file names (why is that forbidden, I LOVE camel case).

Anyways, after renaming my icons and .xml files to all lowercase and then fixing all the references inside the .xml files, voila, R.java was regenerated. Just in time to feel good when I stopped for lunch :-)

Answer 4

You can just delete the R.java file from your project and it will regenerate assuming you have build automatically enabled. If you do not have build automatically enabled simply goto project->build all

Answer 5

In another stackoverflow question, somebody answered this : you must get rid of warnings and errors (syntax and links) in your xml files. This plus doing a clean / build project.

Project -> Clean, and choose the option to build the project.

Answer 6

You can use Eclipse's "Restore from local history" to restore your old R file if it has been deleted. After that you possibly see what keeps Eclipse from building your files (I've seen other errors than before which really helped fixing the problem).